1. Field of the Invention
The present invention is related to the field of communication of telephone type devices through networks, and more specifically to devices, software and methods for detecting an ending of a fax/modem communication between a telephone line and a network.
2. Description of the Related Art
Telephone type devices include telephones, fax machines, modems, and all such devices that can use telephone lines. Some telephone type devices exchange signals that encode voice, while others transfer data.
Telephone lines are increasingly being coupled with networks, such as Local Area Networks (LANs), or global networks. Networks are ideal for carrying data. The data of the telephone line is first changed to data that is transmissible through the network. When the telephone line is connected to a telephone, the data encodes voice. When the telephone line is connected to a fax machine or a modem, the data encodes the fax-type signals or the modem type signals.
A telephone line is typically connected with a network through a device, such as a gateway or a router. If the data encodes fax type signals or modem type signals, then the device preferably operates in the data transfer mode. Such a data transfer mode can be the standard pulse code modulation (PCM) mode. But if the data encodes voice, then the device preferably operates in a favored voice compression mode.
When a connection line is be used to transfer data, the connection can end normally if both parties hang up. Sometimes one of the parties does not hang up, causing the connection to continue to occupy the device of the party and/or telephone connection line. Worse, both of the parties might not hang up, which can also cause the connection to continue to occupy the connection line. This problem can be made more complex when one considers that the parties, after exchanging data, may start using the connection line for a voice conversation. In that case, the device will be operating in the data transfer mode, instead of operating in the compressed mode.
The present invention overcomes these problems and limitations of the prior art.
Generally, the present invention provides devices, software, and methods for detecting when, in a fax/modem type transmission, the transmitted data encode silence or voice. This determines the end of the fax/modem type transmission, after which the device is switched to the more economical voice mode.
The device of the invention is a router or a gateway, coupled between the telephone line and the network. In its preferred embodiment, the device analyzes the energy of the encoded signals. The device discriminates between the type of signals (fax/modem, silence or voice) based on the time patterns of the energy. For fax/modem the pattern is relatively uniform, for silence it is uniformly low, and for voice the pattern oscillates.